Prepared by Amy Dabbs, Horticulture Extension Agent, Charleston County and Joey Williamson, HGIC Horticulture Extension Agent, Clemson University. (New 06/10.)
Foamflower (Tiarella cordifolia) is a shade-loving perennial native to the eastern United States and Canada. This small, evergreen, mounding or running groundcover has been underutilized in the home landscape. Increased development of cultivars and hybrids between eastern and western US native species and an Asian species has created a wide range of tiarellas that are now widely available in the nursery industry. Home gardeners looking for interesting native plants to bring intriguing beauty to shady nooks will enjoy the wide range of new foliage shapes and colors this durable and trouble-free plant has to offer.
Alleghany foamflower (Tiarella cordifolia var. cordifolia)
Joey Williamson, ©2005 HGIC, Clemson Extension
Found in nature on the banks of streams and in moist woodland conditions, these spring bloomers do best in moderate to full shade (with morning sun only). All Tiarella spp. do best in soils high in organic matter where pH ranges from 4.5-7. In South Carolina, foamflowers are more apt to thrive if planted in the mountains or Piedmont regions. They are reportedly hardy in USDA cold hardiness Zones 3-8. Fertilize tiarellas in the early spring with a complete organic fertilizer such as Espoma Holly Tone (4-3-4) or Miracle Gro All Natural & Organic Holly Food (3-4-3).
Blooming begins in early spring along the coast (mid-March) and continues through mid-spring elsewhere in the state. Clouds of foamy white to pink flowers give these plants their common name. They continue to put on their show for 4-6 weeks before fading. However, it is their evergreen, mounding foliage that creates an interesting and eye-pleasing display in the woodland garden throughout the year.
While tiarellas are relatively low growers, reaching 1’-3’ in height and 6”-12” in spread, all can be used effectively in decorative containers and look equally attractive in mass plantings or small groupings. Combine Tiarella with other shade lovers such as hostas, ferns, Solomon’s seal, dwarf crested iris and coral bells (Heuchera sp).
Tiarella species have relatively few pest and disease issues. Slugs and snails are the primary pest problem reported. Foamflowers prefer evenly moist conditions, and established plants will tolerate only brief periods of drought. Foamflowers do not tolerate wet feet, so the planting site must be well-drained. Phytophthora root rot may become a problem in poorly drained clay soils.
Propagate by dividing clumps of Tiarella in late fall. Alternately, rooted runners can be dug and replanted immediately. Tiarella may be started from seed. Seeds germinate quickly, but seedlings may be slow growing.
There is one species of foamflower native to eastern North America. Horticulturally, tiarellas are distinguished by being placed into one of two groupings: T. cordifolia var. cordifolia and T. cordifolia var. collina. The former is commonly called Alleghany foamflower and is characterized by dense clumps of heart-shaped foliage, often with dark burgundy patches on the leaves and white to pale pink flowers. Tiarella cordifolia var. cordifolia spreads by aboveground runners called stolons. Tiarella cordifolia var. collina (synonym T. wherryi) is often called Wherry’s foamflower and forms clumps without runners. This varietal form has more deeply lobed foliage that resembles fig, oak or maple leaves.
Many excellent cultivars of the eastern native foamflower are available, such as:
Numerous new hybrids of foamflower have been produced by crossbreeding the native eastern species (T. cordifolia) with the western US species (T. trifoliata) or the Asian foamflower (T. polyphylla). These hybrids feature many interesting plays on leaf color and shape. Vigorous growth habits with more prolific blooms are also outcomes of the many hybrids and cultivars developed recently. Some exceptional examples include:
The Asian foamflower (T. polyphylla) is native to China, Japan and the Himalayas. It resembles the Alleghany foamflower in appearance, but trials in Georgia indicate it does not perform as well. Likewise, in Georgia trials the western foamflower was less tolerant of the heat and humidity of the South than the eastern species.
Interestingly, horticulturists have created intergeneric crosses between Heuchera spp. and Tiarella spp. to create heucherellas, or foamy bells. These “man made” plants combine the best flowering and foliage characteristics of both plants.
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